In the field of science, especially in microbiology, the need to obtain a representative sample is a constant challenge. It has been often quoted "that a laboratory test is only as good as the sample." This requirement for a representative sample applies, not only to those specimens from a clinical source, industrial processes, or polluted water, but also includes daily operations in the laboratory. For example, a classical microbiological technique is the retrieval and transfer of growth from a tube of nutrient broth. In the usual procedure a loop of growth is removed and streaked on an agar surface or transferred to another tube of broth for further incubation. In some cases a sterile pipette is used instead of a wire loop.
In order to encourage the growth of a wide range of organisms, a small amount of agar (0.1%) may be added to nutrient broth. This amount of agar supports the development of obligate anaerobes, micro-aerophiles and aerobes growing in layers with aerobes at the surface and anaerobes at the bottom of the growth container. If the concentration of agar is increased to a range of 0.16 to 0.4%, subsurface colonies will develop ranging in shape from elongated, diffuse to compact tear shaped. This concentration is generally referred to as soft agar. Microbial growth under these conditions does not readily lend itself to transfer with either a wire loop or pipette, since as the loop or pipette is moved through the layers of growth, contamination occurs before the desired area of growth is reached. There is therefore a definite need in the art for an apparatus for retrieving a representative uncontaminated sample of bacterial growth from specific areas within a growth medium. Subsurface bacterial colony growth in soft agar is further elaborated on in applicant's co-pending patent application, Ser. No. 07/751,182 filed Aug. 28, 1991, now U.S. Pat. No. 5,290,701 and the subject matter of which is incorporated by reference herein.
It is an object of the present invention to provide an improved pipette-syringe combination that permits retrieval of organism samples in a specific area of growth without prior contamination of the sampling device by surrounding media.
Another object of the present invention is an improved pipette-syringe combination that is operable in agar containing and agar free media.
A further object of the present invention is an apparatus and process for retrieving a representative sample from subsurface growth in a media source.
An additional object of the present invention is an apparatus capable of recovering organisms at various depths in water columns of eco-systems.
Still another object of the present invention is a novel liquid sampling device for the collection of liquid samples from various depths of samples or containers of polluted water, fermentation liquids, food processing operations, and the like.
Another object of the present invention is a novel sampling pipette that also can serve as a growth chamber for the collected sample.
Yet another object of the present invention is a process of obtaining a representative sample in a pipette, adding nutrient broth to the pipette and incubating the sample in the nutrient broth containing pipette before transferring the accumulated culture growth to a number of tubes.